A Low-Cost Lightweight Entropic Alloy with High Strength

In this study, a series of lightweight Al–Mg system entropic alloys containing Zn, Cu, and Si were designed based on the order/disorder or entropy, and eutectic concepts. The alloys of Al_58.5Mg_31.5Zn_4.5Cu_4.5Si₁; Al₆₃Mg₂₇Zn_4.5Cu_4.5Si₁; Al_66.7Mg_23.3Zn_4.5Cu_4.5Si₁; Al₈₀Mg₁₄Zn_2.7Cu_2.7Si_0.6; Al₈₅Mg_10.5Zn_2.025Cu_2.025Si_0.45; and Al₉₀Mg₇Zn_1.35Cu_1.35Si_0.3 were prepared by induction melting under a high-purity argon atmosphere and then casted into stainless steel molds. The microstructures which were tested in the as-cast state exhibited multiphases and contained apparent volume fractions of intermetallic compounds and solid solutions. Then, the compressive mechanical properties of the alloys were measured, and high fracture strengths of 577, 677, 590, 498, 814, and 794 MPa, respectively, were determined. Strong hardening phenomena were observed in the Al₈₀Mg₁₄Zn_2.7Cu_2.7Si_0.6, Al₈₅Mg_10.5Zn_2.025Cu_2.025Si_0.45, and Al₉₀Mg₇Zn_1.35Cu_1.35Si_0.3 alloys at room temperature, with amazing plasticity percentages of 13.8, 24.8, and 32.7%, respectively. The property differences in the lightweight alloys were analyzed using the following parameters: the critical values of the enthalpy of mixing; atomic size differences; ratio of entropy to enthalpy; valence electron concentration (VEC); and Pauling electronegativity difference. Finally, three of the aforementioned parameters (atomic size difference, enthalpy of mixing, and Pauling electronegativity difference) were regarded in this study as the crucial rules for the lightweight multicomponent alloys.